Revert "debugger: improve expansion behaviour of pinned tooltips."

This reverts commit 89cee4313c,
as part of the patch breaks QTCREATORBUG-7277.

The GDB case should not filter the Locals model, but the Tooltip model
to display tooltips. CDB has no choice, as the tooltips are expressions,
i.e. cannot be handled, so using the Locals as fall back there is ok.

Change-Id: I196bc683e06f68301bd86aa6fcce14ad2e8c5774
Reviewed-by: Eike Ziller <eike.ziller@nokia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>

src/plugins/debugger/cdb/cdbengine.cpp

@@ -561,6 +561,7 @@ bool CdbEngine::setToolTipExpression(const QPoint &mousePos,
     }
     DebuggerToolTipWidget *tw = new DebuggerToolTipWidget;
     tw->setContext(context);
+    tw->setDebuggerModel(LocalsWatch);
     tw->setExpression(exp);
     tw->acquireEngine(this);
     DebuggerToolTipManager::instance()->showToolTip(mousePos, editor, tw);